1. Field of the Invention
The present invention relates to inks and, more particularly, to fluorescent inks.
2. Background Information
In the machine processing of various types of substrates, such as tickets, labels, postage imprints, and tags, it is generally known to employ detectors which are responsive to colors, and in many cases to the fluorescent emissions of an ink which may be the result of ultraviolet light excitation. For example, in the postage meter art, a red fluorescent ink is often provided for the machine reading of processed mail. Fluorescent colored inks are those in which the ink exhibits a first color, such as blue, black or green, in the visible spectrum and a second color when subjected to ultraviolet light.
Certain drawbacks exist with some prior fluorescent inks. For example, some are made with fluorescent dyes, resulting in prints that are fugitive to light and water. It is also difficult to obtain stable, non-clogging dispersions with some fluorescent inks.
Accordingly, there is a need for improved fluorescent ink jet inks.